This invention relates in general to the production of paper sheet products and is more particularly concerned with improvements in the production of non-laminated paper sheet products having regions of increased thickness for more economical use of the paper products and for conservation of wood pulp.
It has been customary in paper making to attempt to control the thickness of the web being formed to be as uniform as possible in thickness. Thus, sheets of paper cut from the web in either the wet or dry papermaking processes are usually of quite uniform thickness when the paper is viewed in its entirety. Upon much closer investigation, such as under microscopic viewing, differences in thickness are inherent since the pulp fibers cannot be so uniformly laid or dispersed during the papermaking processes so as to avoid any thickness variation on the microscopic level.
Various processing techniques are also known to the prior art to give uniform thickness sheet paper differing or modified characteristics. For example, softer texture can be imparted to relatively thin sheet paper by creping the paper, as by removing the paper from a calendar roll by a doctor. Such processing techniques after the paper has been formed have also been concerned with creating a finished product which has a generally uniform overall appearance.
Usage of paper, on the other hand, does not generally require that the paper be of entirely uniform thickness. For example, paper towels are more frequently used in the center portion than at the edges, especially in soaking up small spills and in drying one's hands. Similarly, in the printing industry, sheets of paper are printed primarily in the center portion such that the margins could be of reduced thickness to reduce the amount of wood pulp and other raw material utilized. Significant amounts of energy could also be conserved in the manufacture of paper of non-uniform thickness with additional energy savings gained in the transportation and further processing of such paper.
The concepts of the present invention could also be utilized to provide increased strength and support in the thicker portions of the paper sheet without the need for special or extra apparatus to add or inject high-strength fibers into the paper web as it is being formed. For example, it has been customary in the manufacture of heavy-duty paper bags suitable for containing and carrying groceries to manufacture such bags from multiple layers or plys of paper sheet stock, each sheet being of uniform thickness. There is, of course, a considerable waste of wood pulp in manufacturing these bags since the same paper thickness is not needed throughout the bag. With the present invention increased thicknesses of pulp can be provided along the areas or points of stress, such as along seams, creases and the top opening of the bag. The balance of the bag can be of reduced thickness of paper for considerable wood pulp savings.
Conversely, the present invention can be utilized to make paper thinner in desired areas by laying less pulp to provide other characteristics, such as increased flexibility along folded portions of the paper where the paper is otherwise of sufficient strength.
It is, therefore, a principal object of the present invention to provide novel and improved apparatus and methods for the manufacture of non-laminated paper sheet stock having regions of increased thickness to reduce the wood pulp requirements in manufacturing paper and thereby conserve wood pulp.
Another object of the invention is to increase the utilization of wood pulp by providing regions of extra thickness, strength and absorbability at those locations in paper sheet stock where the paper is most used.
A further object is to conserve energy by reducing the thickness and weight of the paper in those locations where the paper sheet is least used thereby requiring less energy to dry, transport or further process the paper.
Yet another object is to provide means for automatically depositing extra pulp in locations on the web being formed by either wet or dry papermaking machines such that the areas of increased thickness are an integral part of the paper web and the resultant paper sheet product does not substantially lose its inherent flexibility as in laminated paper products.
Another object of the invention is to provide means for automatically controlling the deposition of extra pulp being formed by the papermaking machine such that the web may be automatically cut into sheets or strips of paper with the areas of increased thickness registered in the desired positions.